1. Field of the Invention
The invention concerns a drive system, especially for a motor vehicle.
2. Description of the Related Art
The invention concerns a drive system, especially for a motor vehicle.
The internal efficiency of internal combustion engine (especially an internal combustion engine with external mix formation; and external ignition) falls off sharply at low effective cylinder mean pressures, and this drop-off is especially pronounced at low rotary speeds. Therefore, high-power engines work only with a relatively poor efficiency when little power is demanded of them relative to their maximum performancexe2x80x94i.e., their effective mean pressure is low.
In order to enhance the efficiency, it has been proposed to shut off individual engine cylinders in such operating conditions; see, for example, xe2x80x9cAutomotive Engineering Handbook,xe2x80x9d published by Robert Bosch GmbH, Dxc3xcsseldorf, 21st Ed., 1991, p. 361. For shutting off cylinders produces a distinct increase in the effective mean pressure in the cylinders not shut off, thus providing a substantial increase in efficiency (indeed, by as much as 30%). Therefore, shutting off cylinders can contribute to an economical use of raw materials and a lessening of the environmental burden of toxic, climate-active, or otherwise harmful exhaust gases.
A switching off of all cylinders of an internal combustion engine in pushing operation is known, for example, from DE-A-38 14 484 (MAI).
The following more remote state of the art shall also be indicated hereafter
The following publications are oriented to devices for active dampening of rotational nonuniformities:
Patent Abstracts of Japan, Vol. 11, No. 28 (M-557), Jan. 27, 1987 and JP-A-61 200 333 (NISSAN I), Patent Abstracts of Japan, Vol. 4, No. 29 (M-002), Mar. 14, 1980 and JP-A-55 005 454 (TOYOTA), EP-A-0 427 568 (ISUZU), DE-A-40 38 301 (HITACHI/NISSAN), EP-A-0 440 088 (NISSAN II), DE-A-32 30 607 (VW I), EP-B-0 175 952 (MAZDA), Patent Abstracts of Japan, Vol. 7, No. 240 (M-251), Oct. 25, 1983 and JP-A-58 126 434 (NISSAN II) and DE-A-41 00 937 (FICHTEL and SACHS).
DE-A-29 02 376 (IVANOV) discloses a device for active dampening of linear oscillations.
EP-A-0 437 266 (MAGNET MOTOR) and DE-B-23 53 724 (HELLING) disclose flywheel accumulators for hybrid vehicles.
DE-A-44 37 322 (VW II) discloses the use of an electric machine as a vehicle brake in an electric or hybrid vehicle.
DE-A-42 25-683 (PFEIFFER) discloses a drive slip control for a rail vehicle
DE-A-32 43 513 (VW ) discloses an electric machine in whose vicinity a coupling is situated.
DE-A-33 38 545 (VW IV) and DE-A-44 08 719 (VW V) disclose electromagnetic couplings.
The invention aims at further developing drive systems with cylinder shutoff.
It accomplishes this goal with a drive system, in particular for a motor vehicle, with:
a multicylinder internal combustion engine;
a device for switching off at least some of the cylinders of the internal combustion engine; and
a device for active reduction of rotational nonuniformities, which is active at least during cylinder shutoff operation in at least certain operating conditions (claim 1). Preferably, the device acts on a shaft, say, the drive shaft of the internal combustion engine or a shaft that is coupled or can be coupled to it (claim 2).
The term xe2x80x9ccylinder shutoffxe2x80x9d is understood here in a broad sense, which embraces all possibilities of operating one or more cylinders no longer actively driving (and no longer using up fuel). This is preferably accomplished by a fuel and possibly an ignition cutoff of the corresponding cylinder, which can be supplemented by a so-called valve shutoff in order to reduce the gas exchange process. Theoretically, a mechanical shutdown of the particular cylinder(s) is also possible. In the literature, the term xe2x80x9ccylinder shutoffxe2x80x9d is also often understood in a narrow sense, namely, in the sense of only the last-mentioned mechanical shutdown, as in the already mentioned xe2x80x9cAutomotive Engineering Handbookxe2x80x9d. But this narrow understanding departsxe2x80x94as mentionedxe2x80x94from the broad understanding employed herein. A special instancexe2x80x94likewise included hereinxe2x80x94is the shutting off of all cylinders of the internal combustion engine in pushing operation. By xe2x80x9cmulticylinderxe2x80x9d is meant, for example, the following numbers of cylinders: 2, 3, 4, 5, 6, 7, 8, 12. The shaft on which the device for reduction of rotational nonuniformity acts is, e.g., the crankshaft itself, namely, its stump at the takeoff side, or a blind stump not transmitting any drive torque. As an alternative, the device can act on a shaft of the drive train, e.g., the drive shaft leading to the transmission at the drive end.
In the state of the artxe2x80x94as already mentionedxe2x80x94there are proposals for devices for active reduction of rotational nonuniformities for internal combustion engines. Their action is based on generating an alternating torque, or also one only pulsating in one direction, which is directed opposite the rotational nonuniformities and which thereby reduces them. Some of these proposals are addressed to the dampening of rotational nonuniformities which occur when idling, such as ISUZU I and HITACHI/NISSAN.
Modem internal combustion engines, such as those used for passenger cars, usually have relatively slight rotational nonuniformities. In practice, therefore, the above proposals have found little application for active dampening of rotational vibration.
The invention concerns a drive system, especially for a motor vehicle, with a multicylinder internal combustion engine, a device for shutting off at least some of the cylinders of the internal combustion engine, and a.,device for active reduction of rotational nonuniformities, acting in particular on a shaft, such as a drive shaft of the internal combustion engine, or a shaft that is coupled or which can be coupled to it, which is active at least during cylinder shutoff mode, at least for certain operating states. The invention is also addressed to a method of operating such a drive system.